Welcome, there are many talented and generous builders on this site. I recommend that you look over a lot of the veteran as well as some of the newer builders as they have a wealth on knowlege. Great thing about living in South FL is that you can build year round. I started mine in Oct of 08 and finished around the following Jan.

Walt,
I think what you are proposing is a rectangular oven 3'X6' with a 3' height with 2" thick walls. That is much bigger than anything anybody on this site is building for home use. It sounds like you are planning on refractory cement for the inside of the oven, then a layer of insulation with rebar in it, and fire bricks on the outside. Your insulating layer needs to be on the outside of the oven, then either firebricks or refractory cement for the inside of the oven, but not both. My recommendation is to download the free Pompeii plans, read them thoroughly then adapt the concepts to a rectangular oven if that is what you are intent on. Good luck.
Eric

mmm no...
Im not explain well my complete idea becouse that not was the question, but, if you divide in 4 a half oval/circle , the sizes of each part Of the dome, " I want to do " , will be around 3 foot from one edge to another edge, and I will do that, with a pre-cast/framework/molds and mortar with Leca.

The outside of this parts I want to do it with mortar cement Type N plus Leca, that make each pice light , also on the inside side of each part I will apply a coat / layer of refractory mortar ( type N plus fireclay) and thin fire bricks on this coat.

I already download the free manual. Also already have the firebricks, fireclay and fiber to reinfore the mortar.

But im asking about the mortar proportion of the Lightweight concrete, it is made with Leca, and also the leca is an insulator (%50 more insulation).

For the heart of the oven I not have problem, only is with the dome, I want to know, or some advices, if this idea will work, and also the proportions of the Leca I need will use, I think is 2. Also if I replace the leca for perlite or vermiculite I will have the same results ( lightweight and insulation).

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